Runners cross the Verrazano-Narrows Bridge shortly after the start of the New York City Marathon in New York, November 2, 2014. (Photo by Lucas Jackson/Reuters)

In this October 18, 2015 photo, contestant Carlos Angevil, Miss Gay Vargas, competes in the swimsuit category of the ninth annual Miss Gay Venezuela beauty pageant in Caracas, Venezuela. Miss Gay Venezuela requires contestants be younger than 37 and be at least 1.7 meters (5' 6" feet) tall. (Photo by Ariana Cubillos/AP Photo)

A Muslim boy prepares plates of food for an Iftar (breaking of fast) meal inside a mosque during the holy month of Ramadan in Ahmedabad, India, June 28, 2015. (Photo by Amit Dave/Reuters)

The Greenland ice sheet is a vast body of ice covering 660,235 sq miles, roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic Ice Sheet. Some scientists predict that climate change may be near a "tipping point" where the entire ice sheet will melt in about 2000 years. If the entire 2,850,000 cubic kilometres (683,751 cu mi) of ice were to melt, it would lead to a global sea level rise of 7.2 m (23.6 ft).

Sally Gomez drives to rescue of friend Michele Moore in flooded parking lot at Hyannis, Mass., September 9, 1969, after torrential rains of Hurricane Gerda flooded low areas of Cape Cod. Ann Davis of Osterville stands up in roof opening to lend a hand. Sally and Michele are from Centerville on the Cape. (Photo by Frank C. Curtin/AP Photo)

A policeman kick in the door of a residence next to the Black Panther headquarters in New Orleans as they moved in following a shootout, September 15, 1970. Other heavily armed policemen stand at ready. (Photo by Jack Thornell/AP Photo)

Soldiers try to attach the balloon to their car, June 1944. (Photo by Jared Enos/Mediadrumworld.com)

A boy dressed as Hindu Lord Shiva poses before performing in a religious procession at the Mahashivratri festival in Allahabad, India, March 7, 2016. Hindus across the country celebrate Mahashivratri, better known as Lord Shiva's wedding anniversary. (Photo by Jitendra Prakash/Reuters)